Power supply having high power factor and low standby power consumption

ABSTRACT

A power supply circuit includes: an anti-electromagnetic interference circuit configured to receive input alternating current power and to output filtered alternating current power; a rectifier circuit configured to rectify the filtered alternating current power; a current correction circuit configured to perform passive power factor correction on the rectified alternating current power; a single-ended flyback converter circuit coupled to the output of the current correction circuit; and a dimming control circuit coupled between the output of the single-ended flyback converter circuit and a light load, wherein the current correction circuit is configured to control a waveform of the rectified alternating current power to follow a current output to the light load in order to provide passive power factor correction.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.15/153,608, filed on May 12, 2016, which claims priority to ChinesePatent Application No. 201521028180.0, filed in the State IntellectualProperty Office of the People's Republic of China on Dec. 11, 2015 andpriority to Chinese Utility Model Patent Application No. 201510917091.X,filed in the State Intellectual Property Office of the People's Republicof China on Dec. 11, 2015, the entire disclosures of which areincorporated herein by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to powerelectronics, more specifically power electronics having high powerfactor and low standby power consumption.

2. Related Art

One comparative design of a single-ended flyback converter circuitcannot achieve power factor greater than 0.7. Another comparative designincludes active power factor correction (APFC) and a single-stage or adouble-stage single-ended flyback converter circuit, but this circuitalso has limitations and may be unable to meet energy efficiencystandards such as no-load power consumption of less than 0.1 W.Therefore, comparative circuit designs may not be able to meet variouspower consumption design requirements imposed by current standards(e.g., California Energy Commission standards for efficiency of portableluminaries and U.S. Department of Energy (DOE) Level VI standards).

SUMMARY

Aspects of embodiments of the present invention are directed to asingle-ended flyback converter circuit with passive power factorcorrection (PPFC) circuit capable of achieving no-load power consumptionless than 0.1 W, and the power efficiency of greater than 81.81%.

According to one embodiment of the present invention, a power supplycircuit includes: an anti-electromagnetic interference circuitconfigured to receive input alternating current power and to outputfiltered alternating current power; a rectifier circuit configured torectify the filtered alternating current power; a current correctioncircuit configured to perform passive power factor correction on therectified alternating current power; a single-ended flyback convertercircuit coupled to the output of the current correction circuit; and adimming control circuit coupled between the output of the single-endedflyback converter circuit and a light load, wherein the currentcorrection circuit is configured to control a waveform of the rectifiedalternating current power to follow a current output to the light loadin order to provide passive power factor correction.

The current correction circuit may include: a first discharge circuitincluding a first electrolytic capacitor coupled in series with a firstdiode and a first node between the first electrolytic capacitor and thefirst diode; a second discharge circuit including a second electrolyticcapacitor coupled in series with a second diode and a second nodebetween the second electrolytic capacitor and the second diode, thefirst discharge circuit and the second discharge circuit being coupledin parallel across an output of the rectifier circuit; and a third diodecoupled between the first node and the second node.

The single-ended flyback converter circuit may include: a power supplycontroller; an output transformer coupled to the power supplycontroller; a secondary transformer coupled to the output transformer;an optocoupler coupled between the power supply controller and thesecondary transformer; and a dimming control circuit coupled to thesecondary transformer and configured to provide dimming control.

The single-ended flyback converter circuit may further include: an RCDsnubber circuit coupled between the current correction circuit and theoutput transformer and coupled to the power supply controller.

The RCD snubber circuit may include: a first resistor; a secondresistor; a capacitor; and a diode, wherein the first resistor, thesecond resistor, and the capacitor are coupled in parallel between thecurrent correction circuit and a cathode of the diode of the RCD snubbercircuit, and wherein an anode of the diode of the RCD snubber circuit iscoupled to the power supply controller.

The dimming control circuit may include: a three-terminal integratedvoltage regulator; a dimming controller coupled to the three-terminalintegrated voltage regulator; a MOS transistor; and a load outputterminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateexemplary embodiments of the present invention, and, together with thedescription, serve to explain the principles of the present invention.

FIG. 1 is a block diagram of energy-saving circuitry according to oneembodiment of the present invention;

FIG. 2 is circuit diagram illustrating an anti-electromagneticinterference circuit and the rectifier circuit according to oneembodiment of the present invention;

FIG. 3 is a circuit diagram illustrating a current correction circuitaccording to one embodiment of the present invention;

FIG. 4 is a circuit diagram illustrating a single-ended flybackconverter circuit according to one embodiment of the present invention;

FIG. 5 is a circuit diagram illustrating a dimming control circuitaccording to one embodiment of the present invention.

DETAILED DESCRIPTION

In the following detailed description, only certain exemplaryembodiments of the present invention are shown and described, by way ofillustration. As those skilled in the art would recognize, the inventionmay be embodied in many different forms and should not be construed asbeing limited to the embodiments set forth herein.

Referring to the block diagram of FIG. 1, a high power factor, ultra lowstandby power consumption energy-saving circuit includes, starting froman input terminal, sequentially connected blocks from ananti-electromagnetic interference (EMI) circuit 10, a rectifier circuit20, a current correction circuit 30 (which may be considered a powerfactor correction or PFC circuit, and which may perform passive powerfactor correction or PPFC on the input power), a single-ended flybackconverter circuit 40, a dimming control circuit 50, where the output ofthe dimming control circuit 50 is connected to a load 70 (e.g., a lightemitting diode light bulb), where the PPFC by the current correctioncircuit 30 controls the input current to follow output waveform changingcircuit in order to reduce the output current waveform distortion.

As shown in FIG. 2, in one embodiment of the present invention, theinput terminal of the anti-electromagnetic interference circuit 10 isconnected to AC power through terminals IN1 and IN2, where fuse F1 isconnected between the two input terminals IN1 and IN2. A capacitor C1 iscoupled in parallel with resistors RL1, RL2 and in series withinductance L1 to form an RLC (or RC) filter circuit, and the output ofthe filter circuit 10 is connected to a rectifier circuit 20 (e.g.,terminals labeled 1 and 3), which includes a full bridge rectifiercircuit D1, which has output terminals 2 and 4.

As shown in FIG. 3, according to one embodiment of the presentinvention, the PPFC by the current correction circuit 30 includes afirst discharge circuit and a second discharge circuit coupled inparallel between the output terminals 2 and 4 of the rectifier circuit20 and between the input terminals A and B of the converter circuit 40(e.g., the current correction circuit 30 has outputs connected to theinput terminals A and B of the converter circuit 40), where a firstdischarge circuit includes an electrolytic capacitor C2 connected inseries with a diode D2 (e.g., the diode D2 is directly connected to thecapacitor C2), and where the second discharge circuit includes anelectrolytic capacitor C16 connected in series with a diode D4 (e.g.,the capacitor C16 is directly connected to the diode D4). A first noden1 is between the electrolytic capacitor C2 and the diode D2 of thefirst discharge circuit, and a second node n2 is between theelectrolytic capacitor C16 and diode D4. A diode D3 connects (e.g., isdirectly connected to) nodes n1 and n2 between the first dischargecircuit and the second discharge circuit.

After the input power is rectified by the rectifier circuit 20, therectified positive half cycle current is input through the capacitor C2,the diode D3, and the capacitor C16, thereby charging the two capacitorsC2 and C16. After reaching a positive half cycle peak, the capacitor C2and the auxiliary discharge diode D2, together with the rear-stagecircuit, form a discharge circuit, and the capacitor C2 discharges untilthe voltage drops to ½ VCC (VCC defined as the total voltage across twofully charged capacitors C2 and C16), at which time capacitor C2 stopsdischarging, but, at this time, capacitor C16 and diode D4 and therear-stage circuit form a discharge circuit, capacitor C16 startsdischarging. As such, the current correction circuit 30 discharges twocapacitors alternately, so that the input current waveform can becontinuous, in order to reduce the current distortion, and therebyachieve a power factor greater than 0.7.

In addition to the above discussion, embodiments of the presentinvention are also directed to a whole circuit proving a high powerfactor through the application of PPFC specific programs by the currentcorrection circuit 30 and a single-ended flyback converter circuit 40which are combined to form a control circuit core.

A comparative design of a single-ended flyback converter circuit withlow PFC generally cannot achieve a power factor greater than 0.7 andtherefore cannot meet certain regulatory standards. For example, theCalifornia Energy Commission (CEC) 2015 Appliance Efficiency Regulations(July 2015, CEC-400-2015-021), which require the power factor forportable LED luminaries and portable luminaries with LED light engineswith integral heat sink, labeled or sold for residential use, to begreater than or equal to 0.70 (see California Code of Regulations, Title20 § 1605.3(n)(3), Table N-2). Another comparative circuit design of asingle-stage or double-stage single ended flyback converter circuitincludes an active power factor correction (APFC) circuit. Although thisarrangement can achieve high power factor correction, the minimum powerrequirements of such a circuit are around 0.2-0.3 W, and therefore thesecircuits cannot achieve less than 0.1 W of power consumption in ano-load state, and therefore cannot meet certain energy efficiencystandards (e.g., the above CEC Regulations or the U.S. Department ofEnergy (DOE) Level VI energy efficiency standards).

A circuit according to embodiments of the present invention uses PPFC toachieve high power factor correction and also uses the currentcorrection circuit 30 which has low loss (e.g., far less than 0.1 W,and, in the ideal state, can be considered to have no loss). At the sametime, the rear stages do not need to end with a power factor correctedsingle ended flyback converter circuit 40, due to high resistance andvery low static losses. After the circuit starts, there is substantiallyno energy consumed under no load conditions. Therefore, it is possibleto achieve, under no-load conditions, a load loss of less than 0.1 W,coupled by the current correction circuit 30 providing PPFC, the totalloss provided by the current correction circuit is less than 0.1 W, andtherefore embodiments of the present invention can meet the energyefficiency standards such as the Level VI standards of the U.S.Department of Energy and the California Energy Commission regulationsfor portable luminaries.

Referring to FIG. 4, the single ended flyback converter circuit 40according to one embodiment of the present invention includes a powersupply controller IC1 coupled to an output terminal of the outputtransformer T1, optocoupler IC2, and peripheral basic electroniccomponents. The output transformer T1 is connected, through secondarytransformer T2, to dimming control circuit 50, which provides theworking voltage of the dimming control circuit 50 and the drivingvoltage of the load 70. The output is fed back to output transformer T1(e.g., through the power supply controller IC1) via optocoupler IC2,which provides optical isolation between the output and the primary sideof the output transformer T1 (and the power supply controller IC1). Thesingle ended flyback converter circuit 40 is coupled to the output ofthe current correction circuit 30 via input terminals A and B (e.g., thesingle ended flyback converter circuit 40 receives input power from thecurrent correction circuit 30).

In addition, the single-ended flyback converter circuit 40 also includesa resistor capacitor diode (RCD) snubber circuit 60 configured to absorbvoltage spikes, where the RCD snubber circuit 60 is connected betweenthe output terminal of the PPFC 30 and the input end (or primary side)of the output transformer T1, and is also connected to the power supplycontroller IC1.

The RCD snubber circuit 60 includes resistor R5, resistor R6, capacitorC6, and diode D5, where resistor R5, resistor R6, and capacitor C6 areconnected in parallel between the output terminal of the currentcorrection circuit 30 and the cathode of diode D5, where the anode ofdiode D5 is connected to the power supply controller IC1.

As shown in FIG. 5, according to one embodiment of the presentinvention, the dimming control circuit 50 includes the sequentiallyconnected blocks including a 3-terminal integrated voltage regulatorIC3, a dimming controller IC4, and a metal oxide semiconductor (MOS)transistor Q1 coupled to the load output terminal SIP2, along withperipheral basic electronic parts. The three-terminal positive regulator(or three-terminal integrated voltage regulator) IC3 converts the powerVCC to the working voltage required by the dimming controller IC4 (e.g.,5V) and through the conduction arising from the control of the MOStransistor Q1 by the dimming controller IC4, the load output of thepower supply to the light (e.g., an LED light bulb) is supplied throughthe load output terminal SIP2.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, but, on the contrary, isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims, andequivalents thereof.

What is claimed is:
 1. A power supply circuit comprising: ananti-electromagnetic interference circuit configured to receive inputalternating current power and to output filtered alternating currentpower; a rectifier circuit configured to rectify the filteredalternating current power; a current correction circuit configured toperform passive power factor correction on the rectified alternatingcurrent power; a single-ended flyback converter circuit coupled to theoutput of the current correction circuit, the single-ended flybackconverter circuit comprising: a power supply controller; an outputtransformer coupled to the power supply controller; a secondarytransformer coupled to the output transformer; and an optocouplercoupled between the power supply controller and the secondarytransformer; and a dimming control circuit coupled between the output ofthe single-ended flyback converter circuit and a light load, the dimmingcontrol circuit being coupled to the secondary transformer, wherein thecurrent correction circuit is configured to control a waveform of therectified alternating current power to follow a current output to thelight load in order to provide passive power factor correction.
 2. Thepower supply circuit of claim 1, wherein the single ended flybackconverter circuit further comprises an RCD snubber circuit coupledbetween the current correction circuit and the output transformer andcoupled to the power supply controller.
 3. The power supply circuit ofclaim 2, wherein the RCD snubber circuit comprises: a first resistor; asecond resistor; a capacitor; and a diode, wherein the first resistor,the second resistor, and the capacitor are coupled in parallel betweenthe current correction circuit and a cathode of the diode of the RCDsnubber circuit, and wherein an anode of the diode of the RCD snubbercircuit is coupled to the power supply controller.
 4. The power supplycircuit of claim 1, wherein the current correction circuit comprises: afirst discharge circuit comprising a first electrolytic capacitorcoupled in series with a first diode and a first node between the firstelectrolytic capacitor and the first diode; a second discharge circuitcomprising a second electrolytic capacitor coupled in series with asecond diode and a second node between the second electrolytic capacitorand the second diode, the first discharge circuit and the seconddischarge circuit being coupled in parallel across an output of therectifier circuit; and a third diode coupled between the first node andthe second node.
 5. A power supply circuit comprising: ananti-electromagnetic interference circuit configured to receive inputalternating current power and to output filtered alternating currentpower; a rectifier circuit configured to rectify the filteredalternating current power; a current correction circuit configured toperform passive power factor correction on the rectified alternatingcurrent power; a single-ended flyback converter circuit coupled to theoutput of the current correction circuit; and a dimming control circuitcoupled between the output of the single-ended flyback converter circuitand a light load, the dimming control circuit comprising: athree-terminal integrated voltage regulator; a dimming controllercoupled to the three-terminal integrated voltage regulator; a MOStransistor; and a load output terminal, wherein the current correctioncircuit is configured to control a waveform of the rectified alternatingcurrent power to follow a current output to the light load in order toprovide passive power factor correction.
 6. The power supply circuit ofclaim 5, wherein the single-ended flyback converter circuit comprises: apower supply controller; an output transformer coupled to the powersupply controller; a secondary transformer coupled to the outputtransformer; and an optocoupler coupled between the power supplycontroller and the secondary transformer, wherein the dimming controlcircuit is coupled to the secondary transformer, and wherein thesingle-ended flyback converter circuit further comprises an RCD snubbercircuit coupled between the current correction circuit and the outputtransformer and coupled to the power supply controller.
 7. The powersupply circuit of claim 6, wherein the RCD snubber circuit comprises: afirst resistor; a second resistor; a capacitor; and a diode, wherein thefirst resistor, the second resistor, and the capacitor are coupled inparallel between the current correction circuit and a cathode of thediode of the RCD snubber circuit, and wherein an anode of the diode ofthe RCD snubber circuit is coupled to the power supply controller. 8.The power supply circuit of claim 5, wherein the current correctioncircuit comprises: a first discharge circuit comprising a firstelectrolytic capacitor coupled in series with a first diode and a firstnode between the first electrolytic capacitor and the first diode; asecond discharge circuit comprising a second electrolytic capacitorcoupled in series with a second diode and a second node between thesecond electrolytic capacitor and the second diode, the first dischargecircuit and the second discharge circuit being coupled in parallelacross an output of the rectifier circuit; and a third diode coupledbetween the first node and the second node.